Wood Ash in the Garden. By Rosie Lerner,Extension Consumer Horticulturist "The chilly winds of winter will likely keep many a wood-burning stove glowing, leaving stove owners with the ashes to dispose of. Many gardening books advise throwing these ashes in the garden. But what affect do these ashes have on the garden?Wood ash does have fertilizer value, the amount varying somewhat with the species of wood being used. Generally, wood ash contains less than 10%potash, 1% phosphate and trace amounts of micro nutrients such as iron,manganese, boron, copper and zinc. Trace amounts of heavy metals such as lead, cadmium, nickel and chromium also may be present. Wood ashes do not contain nitrogen.The largest component of wood ash (about 25%) is calcium carbonate, a common liming material which increases soil alkalinity. Wood ash has a very fine particle size which causes it to react rapidly and completely in the soil.So although small amounts of nutrients are applied with wood ash, the main effect is that of a liming agent.Increasing the alkalinity of the soil does affect plant nutrition. Nutrients are most readily available to plants when the soil is slightly acidic. As soil alkalinity increases and the pH rises above 7.0, nutrients such as phosphorus,iron, boron, manganese, copper, zinc and potassium become chemically tied to the soil and less available for plant use.Applying small amounts of wood ash to most soils will not adversely affect your garden crops and the ash does help replenish some nutrients. But because wood ash increases soil pH, adding large amounts can do more harm than good. Keep in mind that wood ash which has been exposed to the weather, particularly rainfall, has lost a lot of its potency including nutrients.Specific recommendations for the use of wood ash in the garden are difficult to make because soil composition and reaction varies from garden to garden. Distinctly acidic soils (pH less that 5.5) will likely be improved by wood ash addition. Soils that are slightly acidic (pH 6.0 to 6.5) should not be harmed by the application of 20 pounds per 100 square feet, annually.However, if your soil is neutral or alkaline (pH greater than 7.0), find another way to dispose of the wood ash. If you donÂt know the acidity or alkalinity of your soil, have it tested for pH.Crop tolerance to alkaline soil also should be considered. Some plants such as asparagus and junipers are more tolerant of slightly alkaline conditions than "acid-loving" plants such as potatoes, rhododendrons, and blueberries.Wood ash should never be used on such acid-loving plants" Too much ash can increase pH or accumulate high levels of salts that can be harmful to some plants, so use ashes carefully. Wood ash has a NPK of 0-1-3

Raisemybeds, since you are not, I'm sure, throwing gazillion amounts of wood ash onto your lawn, then there is no reason to not do it. The average homeowner uses fertilizer in the spring to re-vitalize their lawns and in so doing, the nitrogen based fertilizers will acidify the lawn somewhat. It all comes down to just how much, and for how long we keep spreading such fertilizers and to what extent the acidity is raised. Many other factors contribute to this acidity....including "the rain that falls mainly on the plain". So unless you are in the business of burning wood and obtaining ashes from a forest fire, go ahead, throw them onto your lawn; it will give some alkalinity that can neutralize to a small extent what the fertilizers do. To the amount: Don't spread more than 20 lbs of ashes per 1000 square feet. I suggest there are plants that are best given such source of alkaline....and potassium. Iris, peony, clematis are some examples. But, in giving to these plants, I suggest you mix well with the soil and give when the plants are growing....thus, don't spread them ontop of your garden until late spring/early summer and water it in well. Wood ashes, as long as they don't come from treated lumber, are great additions to any compost pile. Store them in plastic bags and use whenever there is ice storms that might blanket over shrubs and trees. Wood ahses thrown over such will often have the ice removed in short order due to the sun's rays and can prevent damage occurring due to weight of the ice. The lawn or garden bed under such dusting of ashes, will often be kept bare of snowcover until such time the amount of snow overpowers what the sun is doing. Great for under the wheels to gain traction. On sidewalks, remove slippery surface. Melts snow in no time.

One thing you might do is dig it up and inspect the roots. The roots should have been opened up and spread out before planting. Whether the plant was balled-and-burlapped or potted, make sure that the plant is getting wet. Rhododendron guru Harold Greer noted: "Quite often a plant will get completely dry and then no matter how much water you apply, the rootball will just keep shedding it. The top of the soil may seem wet, and the soil around the plant may even be very wet, but the actual rootball of the plant is bone dry. This is especially true for newly planted rhododendrons, and it is the major reason for failure, or at least less than great success with that new plant. It is hard to believe that a plant can be within mere inches of a sprinkler that has been running for hours and still be dry, yet it can be SO TRUE!" Most rhododendron and azalea plants sold at nurseries and garden centers are sold in containers or have a root-ball that is covered with burlap. These plants have a potentially serious problem when the roots reach the container and start circling inside the pot. They become pot bound or root bound. These roots must be cut so they don't continue to grow and start strangling other roots. Many apparently healthy plants die when the roots start strangling each other. To prevent this, it is necessary to remove the plant from the container and examine their roots. If the plants appear pot-bound and have a thick, dense mat of fibrous roots along the surface of the root ball, used a knife to make three to six vertical cuts, about 2 inches deep, equally spaced around the sides of the root ball. Then use your hands to gently loosen the roots where cuts were made and pull the roots outward. This process stimulates new root growth and allows water and nutrients to penetrate into the root mass. If the roots are not pot-bound, it is not necessary to slice them with a knife, but it is beneficial to loosen and pull them outward with your hands. When working with roots, make sure the plant is thoroughly watered. Any roots that dry out will die.

Probably worth pointing out that the hydroxides are pretty water soluble. So although wood ash applied directly to the soil will make it more alkaline, the de-acidification will probably be minimized if the ash is composted first. By the time the compost is done, a lot of the hydroxides will have leached out. Still a bit worrisome for already alkaline soil, though. The videos do make the good point about alkalinity, and the need to know soil pH before using wood ash.